Vacutainer with positive separation barrier

ABSTRACT

Apparatus providing a physical barrier between the phases of a two-phase liquid, such as whole blood stratified into a serum phase and a cells phase, which includes a transparent tubular receptacle having a rigid wall capable of holding a vacuum. The receptacle has an internal constriction for receiving a resilient plug, which divides the receptacle into an upper chamber and a lower chamber. In the preferred embodiment, the plug has a lower portion, a neck portion and an upper portion. The end of the lower portion is shaped to provide an open pocket for holding a volume of air. A rod of suitable length is detachably mounted through the upper portion of the plug to enable one to urge the plug through the serum in the upper chamber and in sealing engagement with the constriction. The air entrapped in the pocket at the lower portion of the plug creates a slight increase in pressure in the lower chamber as the plug is deformably urged into sealing engagement with the constriction thereby sealingly urging the lower portion of the plug against the constriction. The rod is thereafter detached from the plug and the serum may be asperated out or decanted for analysis, or the open end of the receptacle may be sealed with a stopper thereby making the receptacle ready for use, storage or transportation.

Glover et al.

[451 Apr. 22, 1975 VACUTAINER WITII POSITIVE SEPARATION BARRIER [57]ABSTRACT I t dP.G 'M' P.0 [75] men ors gg vg E Apparatus providing aphysical barrier between the phases of a two-phase liquid, such as wholeblood [73] Assignee: Eastman Kodak Company, stratified into a serumphase and a cells phase, which Rochester, NY. includes a transparenttubular receptacle having a [22] Filed Aug 17 1973 rigid wall capable ofholding a vacuum. The receptacle has an internal constriction forreceiving a resilient [2]] Appl. No.2 389,275 plug, which divides thereceptacle into an upper chamber and a lower chamber. In the preferredem- [52] U S 2l0/5l6 210/1316 210mm 24 bodiment, the plug has a lowerportion, a neck portion [51] Bold 21'/26 and an upper portion. The endof the lower portion is 58 Field 55555162151655 DIG: 24 516-518 shaped PM l 8 210/443 446 361 35983 233/2 2 ume of air. A rod of suitable lengthrs detachably 26 l l 23/259. 5 3 2 mounted through the upper portion ofthe plug to enable one to urge the plug through the serum in the upperchamber and in sealing engagement with the [56] Reterences Citedconstriction. The air entrapped in the pocket at the lower portion ofthe plug creates a slight increase in UNITED STATES PATENTS pressure inthe lower chamber as the plug is deform- 3,508,653 4/1970 ColemanZlO/DIG. 23 ably urged into sealing engagement with the constric- 3647,070 3/1972 Adler 210/516 n thereby Sealing, urging the lower portionof the 3.66l,265 5/l972 Greenspan 310/226 p g against the constrictionThe rod i thereafter firm/er g tached from the plug and the serum may beasperated 3782548 {/1974 31:; ZIOIDIG' 23 out or decanted for analysis,or the open end of the 3 786 985 1/1974 BlaivasI:::::::::::::::::::::235/26 receptacle may be Sealed with a Stopper thereby ing thereceptacle ready for use, storage or transporta- PrimaryE.\'aminer-Charles N. Hart Assistanl Examiner-F. F. Calvetti Attorney,Agent, or Firm-D. M. Schmidt 7 Claims 8 Drawing Figures 32 l 39 I 2| 20a 24 .I '23 22 1 PATENIEDAPRZZIQTS sum 1 of 2 FIG.

VACUTAINER WITH POSITIVE SEPARATION BARRIER BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates generally toapparatus for the physical separation of one phase from the remainder ofa liquid having at least two phases. More specifically. it relates tothe separation by a physical barrier of blood serum from blood cellsafter the blood has been stratified, e.g., by centrifugation, in atubular receptacle.

2. Description of the Prior Art The analysis of blood serum or plasma,extracted from whole blood, is an invaluable tool to the medicalprofession in diagnosing and treating a multiplicity of human disordersand diseases. The separation of this blood serum or plasma from wholeblood is an important step in arriving at a correct medical analysisfrom which proper medication or treatment can be prescribed. Currently,a specimen of serum or plasma is obtained by injecting one end of ahollow needle, open at both ends, into an appropriate vein of the donorfollowed by injection of the other end of the needle into an evacuatedtube through a rubber stopper capable of holding a vacuum", the negativepressure in the evacuated tube causes whole blood to flow from the veininto the tube. Ordinarily, such containers are designed to collectapproximately l milliliters of blood, although there are also containersdesigned for collecting milliliters of blood.

Once a specimen of blood has been collected in the stoppered container.if serum is the end product desired for analysis. the technician willremove the stopper and add a clotting agent to the specimen or let theblood stand for some period of time (around one-half hour) to allow theblood to clot. The blood thereafter undergoes centrifugation in the samecontainer to separate the lighter serum from the heavier cells. lfplasma is the desired end product for analysis, an anticoagulation agentis added to the specimen or it is centrifuged immediately uponcollection, before appreciable coagulation occurs. ln either case, theresult of centrifugation is the stratification of blood into a lighterphase and a heavier phase. Since the more usual laboratory practice inblood analysis is to work with serum rather than plasma, the lighterphase of the stratified blood will be assumed to be serum, although itis understood that it could equally be plasma.

Following stratification of the blood into serum and cells. the serum isisolated from the cells by being asperated or decanted from the firstcontainer into a second container. lsolation of the serum is desirableto prevent possible chemical or physical interaction, between the twointerfaced phases, during storage or transportation which could lead toerroneous results in the analysis. Since some turbulance is normallyunavoidable in the process of transferring the serum, a secondcentrifugation may follow to-collect the remaining cells at the bottomof the second container.

Theaforementioned procedure in obtaining serum obviously involves anumber of time consuming steps. More significantly, however, thetransfer of the serum from the first container to the second increasesthe risk of contamination, spillage, and loss of identity of the donor.Therefore, an improved device for separating serum from cells wouldpreferably embody or provide a number of desirable attributes. e.g., (l)obtaining a sample of blood and achieving separation of the two phasesunder sterile conditions; (2) minimizing the risk of loss of identity ofthe donor of the blood throughout the entire clinical process; (3)minimizing the migration of cells once the blood has been stratifiedinto cells and serum: (4) utilizing, storing, or transporting the serumwithout interplay between the serum and the cells; (5) economicfeasibility in manufacturing a disposable device; (6) the ability tophysically separate the container at a particular location determinableby the purpose of the test; (7) rapidity and simplicity in inserting thephysical barrier to separate the serum from the cells.

Recently. some developments in the art have provided devices having someof these attributes. Two such examples are found in US. Pat. Nos.3.508.653 to Coleman and 3,647,070 to Adler. The Coleman patentdiscloses a method and apparatus for urging a piston through the lighterupper phase. to the interface between the serum and the cells. Thecontainer in the Coleman patent is a tubular receptacle of regularcrosssection. The piston is formed of resilient material and has anundeformed cross-section slightly larger than the inner diameter of thetubular receptacle. To position the piston at the interface of the twophases, a force is applied. either by pushing the piston with a rod orthrough centrifugation. which causes the piston to move toward theclosed end of the receptacle while the fluid pressure of the light phasecauses the piston to be deformed sufficiently to allow the liquid toflow around the piston toward the open end of the receptacle. The forceis removed when the piston reaches the interface between the light phaseand the heavy phase of the twophase blood.

The Adler patent also discloses a device in which a physical barrier isformed in a tubular container of regular cross-section at the interfacebetween the lighter phase and the heavier phase of a two-phase liquid.Prior to insertion, the barrier has a cross-section smaller than theinner diameter of the tubular container. lt has a specific gravitygreater than the heavier phase but less than the lighter phase sobarrier sinks through the lighter phase until it reaches the interfaceof the two phases. Thereafter. through chemical reaction with the serum,the barrier expands to form a seal. Also disclosed in the Adler patentis a two-part container assembly including a tube which has a sleeveinsertable therein. The sleeve is generally shaped as a hopper, i.e., itterminates in a generally truncated coneshaped end portion which hasexternal threads for receiving a like'threaded cap. To physicallyseparate the cells from the serum, a plug is provided which is fixedlyattached to one end of a rod; the other end of the rod is fixedlyattached to the inner portion of the stopper. The length of the rod issuch that when the stopper is inserted into the sleeve, the plug isforced into the truncated opening at the bottom of the sleeve therebyproviding a physical barrier between the serum in the sleeve and thecells in the tube. The sleeve is then removed from the tube and thethreaded cap is screwed into the truncated end.

Although the art has been advanced by the Coleman and Adler patents,there remains an opportunity for improvement. For example, in theColeman patent due to the configuration of the piston, a large force.either centrifugal or direct action as with a rod, must be applied inorder to deform the piston so that the serum will flow around it. Thismay entail the necessity of obtaining new centrifugation equipment tocomply with the added force requirement. In the case of using a detachedrod to push the piston. problems may arise in aligning the rod with thecenter of the piston to avoid unequal forces in the piston. as well asin applying the proper deforming force to avoid possible contaminatingspillage. or turbulance which can disturb the compacted cells andcontaminate the serum. The chemically activated barrier formed in theAdler patent has the disadvantage that it is designed to be formed atthe interface between the light and heavy phase of a twophase liquidhaving a particular density differential. For example. if for aparticular purpose. such as to save time, only a small amount of serumis required relative to the amount of whole blood. the density change inthe heavier phase may be insufficient to buoy the barrier at theinterface. Moreover, there is a waiting period in which the physicalbarrier expands to form the seal at the interface. That is. thecontainer must be held in place until the barrier expands to form theseal. This may inconvenience the technician and add valuable time to thetest schedule. Since it is made up of numerous parts, the two-partcontainer disclosed by Adler has the disadvantages of complexity,expense and a multiplicity of handling operations.

Regarding the desirable attributes enumerated above, it is clear thatthe prior art does not disclose or provide a device having all of them.

Accordingly. it is an object of the invention to provide a disposablereceptacle for containing blood stratified into a lighter phase and aheavier phase wherein a physical barrier can be inserted rapidly andeasily to separate the lighter phase from the remaining liquid.

It is another object of the invention to provide a device for physicallyseparating blood serum from the cells wherein no migration of the cellsor contamination of the serum occurs once the physical barrier ispositioned in place.

It is another object of the present invention to provide a disposablereceptacle for the separation ofserum from cells which is economicallyfeasible and simple to manufacture.

It is another object of the invention to provide a disposable receptaclefor the separation of serum from cells in which the location of theconstriction receiving the physical barrier can be varied in manufactureaccording to the purpose of the test.

SUMMARY OF THE INVENTION These and other objects are accomplishedaccording to the preferred embodiment of the present invention byforming a constriction, for sealingly receiving a plug, in a tubularreceptacle used in containing a specimen of blood from a donor. Theconstriction defines an aperture which divides the receptacle into alower chamber and an upper chamber. and which has a crosssectionaldimension smaller than the smallest interior crosssectional dimension ofthe upper chamber of the receptacle. After centrifugation of the blood.the cells are compacted into the lower chamber while the serum remainsin the upper chamber. A plug is then deformingly inserted into theconstriction thereby placing a physical barrier between the lowerchamber and the upper chamber. The resilient plug is symmetrical about acenterline and at its widest diameter is smaller in crosssection thanthe largest internal cross-sectional dimension of the upper chamber/Theplug has a lower portion. a neck portion and an upper portion forsealingly engaging the constriction at. respectively, the lower chamber.the aperture. and the upper chamber. Detachably mounted to the upperportion of the plug, coincident with the centerline thereof, is a rod ofoperative length for urging the plug into sealing engagement with theconstriction, the rod being thereafter removable from the plug.

In one embodiment of the invention, the lower portion of the plug has anundeformed cross'section larger than the aperture of the constrictionand a configuration operatively related to the constriction for guidingthe lower portion of the plug through the aperture and into the lowerchamber in response to a plug deforming force applied through the rod.The neck portion has a cross-section slightly larger than the apertureand is compressed into sealing engagement with the constriction as thelower portion is urged into place in the lower chamber. The upperportion of the plug has a larger cross-section than the neck portion formaintaining the neck portion in sealing engagement with theconstriction. The sealing properties of the plug can be further improvedby forming an open pocket at the end of the lower portion to receive avolume of air and retain it as the plug is urged through the serum andas the lower portion is deformingly urged through the constriction. Theeffect of the trapped air is to increase slightly the pressure in thelower chamber thereby sealingly urging the lower portion of the plugagainst the constriction.

The invention and its objects and advantages will become more apparentin the detailed description of the preferred embodiment presented below.

BRIEF DESCRIPTION OF THE DRAWINGS In the detailed description of thepreferred embodiment of the invention presented below, reference is madeto the accompanying drawings in which:

FIG. I is an isometric view of the preferred embodiment of the inventionshowing a tubular receptacle having a constriction and a resilient plugwith a detachable handle;

FIG. 2 is an enlarged longitudinal cross-sectional view of theconstriction. the other portions of the receptacle cut-away for clarity;

FIG. 3 is a longitudinal cross-sectional view of the plug of thepreferred embodiment showing a breakaway rod and an open pocket at thelower portion of the plug;

FIG. 4 is a cross-sectional view of the receptacle of the inventionfollowing the collection of a specimen of whole blood;

FIG. 5 is a longitudinal cross-sectional view of the receptacle afterthe whole blood has been subjected to centrifugation and the plug isabout to be inserted in the constriction to effect physical separation;

FIG. 6 is an enlarged view of the constriction and plug shown in FIG. 5also showing the deformation of the lower portion of the plug as theplug is urged into sealing engagement with the constriction;

FIG. 7 is a longitudinal cross-sectional view of the receptacle showingthe plug in sealing engagement with the receptacle and the handle beingdetached from the plug thereby effecting physical separation betweenthe.

cells in the lower chamber and the serum in the upper chamber;and

FIG. 8 is a longitudinal cross-sectional view of another embodiment ofthe plug showing a pull-away rod.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawingswherein like referenced numerals have been used in several views andfigures for like elements. FIG. 1 illustrates a tubular receptaclegenerally indicated by reference numeral 10 and a resilient pluggenerally indicated by reference numeral 30, having rod means 35. Thereceptacle is integrally formed with a lower closed end 14 and an upperopen end 13. Upper and "lower" are used throughout this specification inrelation to a tubular receptacle which is parallel to a gravitationalvector. The constriction formed in receptacle l0 divides the receptacleinto an upper chamber 11 and a lower chamber 12. It is common practicein blood analysis to draw approximately l0 milliliters of blood from adonor. Receptacle 10 is designed to accept approximately 10 millilitersof blood and the constriction is positioned such that lower chamber 12has approximately 55 percent of the usable volume and upper chamber 11has the remaining 45 percent. After centrifugation. the compacted cellsnormally make up slightly over 50 percent of the volume. Hence. all thecells will be in the lower chamber 12 leaving only serum in the upperchamber 11. If appropriate. e.g.. where a small amount of serum isneeded relative to the total blood specimen. the relative volume inupper chamber 11 may be reduced by forming constriction 20 closer toopen end 13.

The tubular receptacle can be made from a variety of materials by avariety of manufacturing techniques. both materials and techniques beingwell known in the art and neither forming any part of the presentinvention. For example. it can be made economically from syntheticresinssuch as Plexiglass by. eg, injection blow-molding techniques.Structurally. the receptacle must be capable of withstanding thepressure differential on the walls resulting from the evacuation of airfrom the interior: chemically, it must not appreciably react with theblood; esthetically. it is usually made of a transparent material. Atubular receptacle made of. eg, Plexiglass would satisfy theserequirements since the tubular design would give it the structuralstrength required. the molding material does not react appreciably withblood, and it is transparent. However. a material of substantiallycomparable characteristics would serve as well.

The plug can be formed from a variety of materials, e.g.. rubber. whichare resilient and do not interact chemically with serum or plasma. It isclear that constriction 20 may assume a variety of shapes so long asplug 30, which provides a barrier at the constriction, is formed inoperative relation to the shape of the constriction. For example, thereshould be an obvious relationship between the shape and size of theconstriction at the aperture and that of the plug at the sealing area;similarly. the shape of the constriction in the upper chamber and theend of the plug which first comes in contact with the constrictionshould be so related that the plug can be mechanically guided intoplace. As seen more clearly in FIG. 3, plug 30 in the preferredembodiment includes a lower portion 31 having an open pocket 34, a neckportion 32 and an upper portion 33 from which detachable rod 35protrudes. The toe 38 of rod 35 may be located in upper portion 33,

portion and into the lower portion 31, above open pocket 34 (not shown).The latter location would enable lower portion 31 to stretch in responseto a force transmitted through rod 35, thereby facilitating insertion ofplug 30 into constriction 20. Ordinarily. however, the location of thetoe 38 is determined by such factors as the resilience of the plug, therelative dimensions and configurations of the plug and the constriction.and the manner in which the rod is to be detached from the plug.

In upper chamber 11, constriction 20, terminating in cylindricalaperture 24, flares conically from aperture 24 to meet the interiorcylindrical wall 26 of upper chamber 11. In lower chamber 12, theconstriction steps from cylindrical aperture 24 to cylindrical bore 22whose cross-sectional dimension is greater than that of aperture 24 butordinarily less than that of the interior cylindrical wall 26 of lowerchamber 12. The crosssectional dimension of cylindrical bore 22 isslightly less than that of the largest cross-section of lower portion 31of plug 30 so that lower portion 31, by being slightly compressed. fitssnugly in the lower chamber. The annular wall 29 defined by thedifference between cylindrical aperture 24 and cylindrical bore 22 issealingly engaged by annular shoulder 39 of plug 30 defined by thedifference in cross-section between neck portion 32 and lower portion31. See FIG. 3. Following cylindrical chamber 22, the constrictionflares at 23 to meet interior cylindrical wall 26 of lower chamber 12.

FIG. 4 is a view of the receptacle filled with approximately l0milliliters of whole blood from a donor. The method for drawing blood iswell known in the art and will not be described in great detail.Ordinarily the empty receptacle has a resilient stopper 15 which iscapable of holding a vacuum. One end of a double-ended needle isinjected into a donor and the other end is injected into the evacuatedreceptacle 10 through stopper 15. The negative pressure in thereceptacle draws approximately 10 milliliters of blood, and afterwardsthe double-ended needle is removed first from the receptacle and thenfrom the donor. It is seen that if the evacuated container anddouble-ended needle are sterile, the blood. schematically represented bynumeral 50, will not be contaminated. It should be noted that thestopper, the double-ended needle, and the mechanism for evacuating thereceptacle. form no part of this invention and are presented only in theinterest of clarity and understanding of the invention. However, it iscontemplated that these features will be used in the practice of theinvention.

After obtaining a specimen of blood as shown in FIG. 4, the stopper 15is removed and a clotting agent is introduced into the specimen or thereceptacle is allowed to stand. open to the atmosphere. long enough forcoagulation of the blood to occur. Thereafter. the receptacle undergoescentrifugation until the cells 55 are compacted in the lower chamber 12,as shown in FIG. 5. Upper chamber 11 will then contain pure serum.Alternatively. if plasma is desired rather than serum. the blood may becentrifuged immediately following the collection of the blood in thereceptacle. or an anticoagulation agent may be added to the specimen.

Once the cells are compacted through centrifugation in lower chamber 12as shown in FIG. 5, plug 20 is inserted into the constriction. As seenmore clearly in FIG. 6, as the plug is urged through constriction 20 bya force applied through rod 35, the lower portion 31 of the resilientplug 30 is deformed to comply with the smaller cross-section of apertureThe deformation of lower portion 31 of the plug 30 also allows the flowof a small amount of serum from above the compacted cells in lowerchamber 12 to pass into upper chamber 11 to replace the volume occupiedby lower portion 31 of the plug 30. This flow is schematicallyillustrated in FIG. 6 as arrows 53. The amount of serum that must flowupward is determined by the size of lower portion 31 of plug 30.Normally, the flow is slight and will not cause any disturbingturbulence.

As lower portion 31 of the plug is deformingly urged through theconstriction, the air bubble in open pocket 34 is slightly compressed.The slight increase in pressure in lower chamber 12 created by the airbubble in pocket 34 forces the annular shoulder 39 of lower portion 31of the plug, against the annular wall 29 of the constriction 20. Theresult is a barrier producing a positive seal between the compactedcells 55 in lower chamber 12 and the serum 56 in upper chamber 11. Oncethe plug is seated in position, rod 35 may be twisted and broken off atthe weakened area 37. The handle portion ofthe rod may then be removedand the serum may then be decanted, aspirated, etc. for analysispurposes. Alternatively, stopper 15 may be replaced at the open end ofthe receptacle for shipping and/or storage purposes.

FIG. 8 illustrates another embodiment of the plug 30 of the invention.Plug 30 has the same configuration as plug 30 of the preferredembodiment; detachable handle 40, however, pulls-away rather thanbreaksaway. Conical toe 41 is embedded in the resilient plug and issimply pulled out once plug 30' is sealingly positioned in theconstriction.

It is readily apparent to those skilled in the art that the receptacleand plug of the present invention provides a disposable apparatus forphysically separating stratified blood which: can receive a specimen ofblood under sterile conditions; minimizes the risk of loss of identityof the donor; effectively halts the migration of cells into the lighterphase once the plug has been inserted and prevents chemical interactionbetween the two phases; and which attains physical separation quicklyand easily at a location in the receptacle determined by the location ofthe constriction.

The invention has been described in detail with particular reference toa preferred embodiment thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

We claim:

1. Apparatus for separating with a physical barrier one phase from theremainder ofa liquid having at least two phases, comprising:

a. a tubular unitary receptacle open at one end and closed at theopposite said one end, for containing such liquid,

said receptacle having an internal constriction defining an aperturewhich divides said receptacle into a first chamber for containing suchone phase only and a second chamber for containing the remainder of suchliquid,

said aperture having a cross-sectional dimension smaller than thesmallest internal cross-sectional dimension of said first chamber;

b. a resilient plug for sealingly engaging said constriction to form aphysical barrier between said first chamber and said second chamber,said plug being symmetrical about a centerline and smaller incross-section at its widest diameter than the largest internalcross-sectional dimension of said first chamber, and having a firstportion, a neck portion, and a second portion for engaging saidconstriction at, respectively, said first chamber, said aperture, andsaid second chamber; and 0. rod means detachably mounted through saidfirst portion of said plug in coincidence with said centerline forurging said plug into sealing engagement with said constriction, saidrod means being thereafter removable from said plug. 2. The invention asdefined in claim 1 wherein: said second portion of said plug has anundeformed cross-section at its widest diameter larger than suchcross-sectional dimension of said aperture, and a configurationoperatively related to said constriction for guiding said second portionthrough said aperture and into said second chamber in response to aforce applied through said rod means, said neck portion of said plug hasan undeformed cross-section slightly larger than such crosssectionaldimension of said aperture and being compressable for sealing engagementwith said constriction at said aperture as said second portion is urgedinto place in said second chamber, and

said first portion of said plug has a larger crosssection than said neckportion for maintaining said neck portion in sealing engagement withsaid constriction.

3. The invention as defined in claim 2 wherein said second portion ofsaid plug includes an open pocket at the end remote from said neckportion for receiving a volume of air and retaining said air as saidplug is urged through such one phase of such liquid and as said secondportion is deformingly urged through said constriction.

4. In an apparatus for maintaining separation by a physical barrier of aStratified two-phase liquid, such as a blood specimen followingstratification of the heavier cells from the lighter fluid, of the typehaving a tubular unitary receptacle open at one end and closed at theend opposite said one end, and a resilient plug forming said physicalbarrier, the improvement comprising:

an internal constriction in said receptacle defining an aperture whichdivides said receptacle into a first chamber and a second chamber, andwhich is of smaller cross-sectional dimension than the smallest internalcross-sectional dimension of said first chamber, for receiving saidresilient plug in sealing engagement therewith to form said physicalbarrier separating the lighter fluid in said first chamber from theremaining liquid, which includes said heavier cells, in said secondchamber;

said plug having a first portion, a second portion, and

a neck portion between said first and second portions for engaging saidconstriction at, respectively, said first chamber, said second chamber,and said aperture.

5. The invention as defined in claim 4 wherein said second chambercomprises about 55 percent of the operatively usable volume of saidtubular receptacle.

6. In an apparatus for maintaining the separation by a physical barrierof a stratified two-phase liquid, such as a blood specimen followingstratification of the heavier cells from the lighter fluid, of the typehaving a tubular receptacle. open at one end and closed at the endopposite said one end. with an internal constriction defining anaperture which divides said receptacle into a first chamber and a secondchamber. the improvement comprising:

a. a resilient plug for sealingly engaging said constriction to formsaid physical barrier between said first chamber and said second chambersaid resilient plug being symmetrical about a center line and having afirst portion. a neck portion and a second portion for engaging saidconstriction at. respectively, said first chamber, said aperture. and

said second chamber; and

b. rod means detachably mounted through said upper portion incoincidence with said centerline for urging said plug into sealingengagement with said constriction. said rod means being thereafterremovable from said plug.

7. The invention as defined in claim 6, wherein said second portion ofsaid resilient plug includes an open pocket at the end remote from saidneck portion for re- 0 ceiving a volume of air and retaining said air assaid plug is urged through such lighter fluid of such liquid and as saidsecond portion is urged through said constriction.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIONPATENT NO. 3,879,295

DATED April 22, 1975 INVENTOR(S) Clyde P. Glover and Michael P. O'Neillit is certified that error appears in the above-identified patent andthat said Letters Patent Q are hereby corrected as shown below:

Abstract, line 22, "asperated" should read ---aspirated-,

Column 1, line 52, "perated" should read -pirated---.

+ Column 2, line 66, "provement." should read ---provemnts L Column 7line 3 "apert should read aperature 24.

In the title, "Vaoutainer" should read Evacuated Blood Serum SeparationDevice b Signed and Scaled this seventh Day of Oct-019671975 [SEAL] &Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Parents1nd Trademarks

1. Apparatus for separating with a physical barrier one phase from theremainder of a liquid having at least two phases, comprising: a. atubular unitary receptacle open at one end and closed at the oppositesaid one end, for containing such liquid, said receptacle having aninternal constriction defining an aperture which divides said receptacleinto a first chamber for containing such one phase only and a secondchamber for containing the remainder of such liquid, said aperturehaving a cross-sectional dimension smaller than the smallest internalcross-sectional dimension of said first chamber; b. a resilient plug forsealingly engaging said constriction to form a physical barrier betweensaid first chamber and said second chamber, said plug being symmetricalabout a centerline and smaller in cross-section at its widest diameterthan the largest internal cross-sectional dimension of said firstchamber, and having a first portion, a neck portion, and a secondportion for engaging said constriction at, respectively, said firstchamber, said aperture, and said second chamber; and c. rod meansdetachably mounted through said first portion of said plug incoincidence with said centerline for urging said plug into sealingengagement with said constriction, said rod means being thereafterremovable from said plug.
 1. Apparatus for separating with a physicalbarrier one phase from the remainder of a liquid having at least twophases, comprising: a. a tubular unitary receptacle open at one end andclosed at the opposite said one end, for containing such liquid, saidreceptacle having an internal constriction defining an aperture whichdivides said receptacle into a first chamber for containing such onephase only and a second chamber for containing the remainder of suchliquid, said aperture having a cross-sectional dimension smaller thanthe smallest internal cross-sectional dimension of said first chamber;b. a resilient plug for sealingly engaging said constriction to form aphysical barrier between said first chamber and said second chamber,said plug being symmetrical about a centerline and smaller incross-section at its widest diameter than the largest internalcross-sectional dimension of said first chamber, and having a firstportion, a neck portion, and a second portion for engaging saidconstriction at, respectively, said first chamber, said aperture, andsaid second chamber; and c. rod means detachably mounted through saidfirst portion of said plug in coincidence with said centerline forurging said plug into sealing engagement with said constriction, saidrod means being thereafter removable from said plug.
 2. The invention asdefined in claim 1 wherein: said second portion of said plug has anundeformed cross-section at its widest diameter larger than suchcross-sectional dimension of said aperture, and a configurationoperatively related to said constriction for guiding said second portionthrough said aperture and into said second chamber in response to aforce applied through said rod means, said neck portion of said plug hasan undeformed cross-section slightly larger than such cross-sectionaldimension of said aperture and being compressable for sealing engagementwith said constriction at said aperture as said second portion is urgedinto place in said second chamber, and said first portion of said plughas a larger cross-section than said neck portion for maintaining saidneck portion in sealing engagement with said constriction.
 3. Theinvention as defined in claim 2 wherein said second portion of said plugincludes an open pocket at the end remote from said neck portion forreceiving a volume of air and retaining said air as said plug is urgedthrough such one phase of such liquid and as said second portion isdeforminglY urged through said constriction.
 4. In an apparatus formaintaining separation by a physical barrier of a stratified two-phaseliquid, such as a blood specimen following stratification of the heaviercells from the lighter fluid, of the type having a tubular unitaryreceptacle open at one end and closed at the end opposite said one end,and a resilient plug forming said physical barrier, the improvementcomprising: an internal constriction in said receptacle defining anaperture which divides said receptacle into a first chamber and a secondchamber, and which is of smaller cross-sectional dimension than thesmallest internal cross-sectional dimension of said first chamber, forreceiving said resilient plug in sealing engagement therewith to formsaid physical barrier separating the lighter fluid in said first chamberfrom the remaining liquid, which includes said heavier cells, in saidsecond chamber; said plug having a first portion, a second portion, anda neck portion between said first and second portions for engaging saidconstriction at, respectively, said first chamber, said second chamber,and said aperture.
 5. The invention as defined in claim 4 wherein saidsecond chamber comprises about 55 percent of the operatively usablevolume of said tubular receptacle.
 6. In an apparatus for maintainingthe separation by a physical barrier of a stratified two-phase liquid,such as a blood specimen following stratification of the heavier cellsfrom the lighter fluid, of the type having a tubular receptacle, open atone end and closed at the end opposite said one end, with an internalconstriction defining an aperture which divides said receptacle into afirst chamber and a second chamber, the improvement comprising: a. aresilient plug for sealingly engaging said constriction to form saidphysical barrier between said first chamber and said second chamber,said resilient plug being symmetrical about a centerline and having afirst portion, a neck portion, and a second portion for engaging saidconstriction at, respectively, said first chamber, said aperture, andsaid second chamber; and b. rod means detachably mounted through saidupper portion in coincidence with said centerline for urging said pluginto sealing engagement with said constriction, said rod means beingthereafter removable from said plug.